docs: def repmf(instr, marker, value, sigdig, informat, lenout=None):
      """
      Replace a marker in a string with a formatted double precision value.
  
      http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/repmf_c.html
  
      :param instr: Input string.
      :type instr: str
      :param marker: Marker to be replaced.
      :type marker: str
      :param value: Replacement value.
      :type value: float
      :param sigdig: Significant digits in replacement text.
      :type sigdig: int
      :param informat: Format 'E' or 'F'.
      :type informat: str
      :param lenout: Optional available space in output string.
      :type lenout: int
      :return: Output string.
      :rtype: str
      """
      if lenout is None:
          lenout = ctypes.c_int(len(instr) + len(marker) + 15)
      instr = stypes.stringToCharP(instr)
      marker = stypes.stringToCharP(marker)
      value = ctypes.c_double(value)
      sigdig = ctypes.c_int(sigdig)
      informat = ctypes.c_char(informat.encode(encoding='UTF-8'))
      out = stypes.stringToCharP(lenout)
      libspice.repmf_c(instr, marker, value, sigdig, informat, lenout, out)
      return stypes.toPythonString(out)